Since start of Ukraine's invasion powerful Russian businessmen die in "mysterious circumstances" US intel officer calls it "deliberate stealth tactics"

Powerful Russians continue to turn up dead in an increasingly bizarre series of fatalities following criticism of Russian President Vladimir Putin.

A number of businessmen have turned up dead over the past few months as Russians grow increasingly dissatisfied with the drawn-out invasion of Ukraine, per Fox News.

Ivan Pechorin, a managing director for the aviation industry at the Corporation for the Development of the Far East and the Arctic, on September 12 died after reportedly falling from a speeding boat off the coast of Vladivostok.

Ravil Maganov, chairman of Russian oil giant Lukoil, died after reportedly falling from the sixth-floor window of a Moscow hospital on Sept. 1. He and his company had urged Putin to end the invasion, calling it a "tragedy." Lukoil claimed Maganov "passed away after a severe illness."

Aleksandr Subbotin, a former top manager of Lukoil, was found dead in the basement of a Moscow residence in May after he allegedly visited a healer to cure him of hangover symptoms but instead suffered heart failure.

At least eight other Russian oligarchs have died in strange circumstances over the past few months, according to Euro News. International investigators have suggested looking at the deaths as staged suicides or assassinations as retaliation for their opposition to the Ukraine invasion or links to corruption in Russian gas company Gazprom.

Leonid Shulman, head of the transport service at Gazprom Invest, was found dead in February in the run-up to the invasion. Authorities said they found a suicide note beside the executive, who reportedly slashed his wrists in the bathroom of his St. Petersburg cottage.

The morning after the invasion started, authorities found Alexander Tyulyakov, a senior executive at Gazprom’s Corporate Security, hanging in the garage of his home. An unnamed law enforcement source told the Russian newspaper Novaya Gazeta that Gazprom’s own security unit had arrived ahead of the police.

Rebekah Koffler, a former Defense Intelligence Agency officer and author of "Putin’s Playbook: Russia’s Secret Plan to Defeat America," told Fox News Digital at the time of Pechorin’s death that "the truth is unlikely to be discovered because Russian investigations cannot be trusted."

"If this was a hit job, it would be made to look exactly like a tragic accident," Koffler had explained.

"The truth is these tactics are designed deliberately to be stealthy, so no investigator could identify foul play. They are usually deemed ‘tragic accidents,’ [which is] also part of the doctrine," she said.